1. Field of the Invention
The present invention relates generally to birdhouses, nesting platforms and artificial nesting sites, and more specifically to a self-contained multiple nesting structure offering ideal partial enclosures which cliff swallows may then nearly enclose with their adhesive mud nests. The ideal spacing, size, shape, surface texture and multiple compartments are highly attractive to colonial nesting cliff swallows and protective of their nests against weather and collapse. The orderly, spaced divided arrangement of nests encouraged by the invention permits convenient further protection of nests once built and permits inspection of usually inaccessible nest interiors through correspondingly spaced roof or back access doors. As a self-contained unit, the present invention may be conveniently attached to or removed from the buildings or bridges, etc., on which cliff swallows might otherwise attempt to nest, despite inadequate structure or texture to support their nests.
2. Description of the Prior Art
Cliff swallows once nested only in natural settings such as on the jagged faces of substantially vertical rock cliffs. In such settings, they build their globular bottle-shaped nests in the corner or niche created when a vertical wall intersects a horizontal jag or overhang. Also known as "eave swallows," cliff swallows have adapted to nesting on man-made structures. On the exterior side of a barn or building, cliff swallows will build their adhesive mud nests up into the corner formed by the vertical wall and the horizontal overhang of the eave or soffit. These birds will also nest where structural members intersect vertically and horizontally on bridge understructures.
Cliff swallows are declining or underpopulated in some regions. The replacement of old, unpainted wood barns and bridges with regularly painted modern steel structures has deprived these birds of the rough adhesive nesting surfaces they had adapted to. Collapse of nests from smooth buildings or bridge surfaces is a problem for the species.
One prior art device, described in Nest Boxes for Alberta Birds by Shantz and Pearman, on page 24, to attract cliff swallows and prevent nest collapse, is to attach a board high on the side of a building nailed flat a few inches below the eave. With the narrow edge of the attached board serving as the foundation, swallows will randomly build along its length, also attaching nests to the small section of wall and eave above. While the applied board edge offers some support to the nests, the remaining support structure of the building upper wall and eave may not be sufficiently porous to hold the nests. If nests supported in this way collapse, there is not enough width of the board edge to hold eggs or nestlings. With no vertical dividers, swallows must build side walls as well as the enclosing front wall, with greater expenditure of time in a short breeding season. With no vertical dividers, or no vertical support other than the wall of the building, swallow nests will often be built side by side with shared mud walls. When one nest collapses, adjacent nests may also collapse. Since the nests are built randomly with irregular gaps between nests or groups of nests, and since there are no convenient vertical points of attachment, such as the dividers of the present invention, it would be difficult to attach a protective or supportive band, as is possible with the dividers of the present invention, once nests are built. The present inventor is not aware of any such prior art use of a strap or a band applied to protect existent nests.
With the nests attached directly to non-removable parts of a building, they cannot be taken down for inspection or cleaning without destroying them. Nor can they be inspected in place, nor can traps for destructive competing species be set within the nests, as is possible with the present invention. With nests attached directly to a building, nest parasites may more easily infiltrate interiors used by humans. Randomly located nests may create an untidy appearance, and directly applied nests may degrade paint finishes.
Another prior art artificial nesting opportunity for cliff swallows is one that is not created deliberately. In addition to nesting where the vertical surface of a large beam, or I-beam webbing, meets a horizontal supported surface, or I-beam upper flange, cliff swallows will build their nests between closely spaced upper and lower flanges on small I-beams. On small I-beams, the lower flange may provide a good width for a nest foundation, but the matching upper flange will be far too narrow to support the upward, forward projection of the nest. Only where broader structural surfaces or members cross the top of the supporting small I-beam are cliff swallows offered sufficient nest attachment surface overhead. However, movement by thermal expansion and vehicle vibration may fracture nests attached to two adjacent but separate members or surfaces.
As with the prior art building eave nesting situations already noted, smoothly painted surfaces of bridge I-beams, structural members and surfaces may not be porous or rough enough to hold nests for long. And again, the lack of spaced, supporting vertical walls requires swallows to construct their own weaker, potentially collapsible nests with shared sidewalls. Also, nests attached directly to a bridge or other permanent structure cannot be temporarily taken down, internally inspected in place, or opened for setting a trap for problem species. Further, nests attached directly to bridges degrade paint finishes and nests must be destroyed for bridge painting.
Another prior art cliff swallow nesting situation occurs where a vertical wall intersects a horizontal or downward sloping eave, as previously described, and a projecting rafter end creates an additional supporting vertical wall for the adjacent nest. This nesting situation is shown photographically in Birds Nests by Harrison on page 133. Since the spacing and shape of such building rafters is very wide and not intended to determine the number or orientation of nests built against them or between them, swallows will use, or not use, these non-deliberate niches inefficiently, however they choose, and orient nests in many directions. Aside from the additional vertical wall provided only to one side of only those nests which abut a rafter, this situation shares all the negative aspects of the structurally simpler wall/eave situation described previously.
A similar prior art situation has been recorded photographically in Birds of America (Garden City Publishing 1936) section on Swallows on page 85. A wide horizontal shelf has been permanently attached directly to the side of a barn with two widely spaced support brackets underneath. One nest has been built underneath abutting one bracket, but facing in a sideways direction. A second nest shown does not take advantage of the second bracket and faces a forward direction. With nests partially attached to the side of the barn as well as to the underside of the attached shelf, the structure is not removable for inspection, etc. And aside from the additional nest attachment surface provided only to one side of only those nests which abut a support bracket, this prior art device also shares all the negative aspects of the wall/eave situation described previously.
Other prior art nesting shelves or platforms designed for other species relate somewhat to the present invention. These may be simple, short, relatively wide, horizontal shelves mounted fairly close to overhanging eaves for shelter, as shown in Nest Boxes for Alberta Birds on page 24 or they may be self-contained and more enclosed with a wide floor, fairly high back, wide roof, partial or complete sides and open front. These are intended for species which do not build the nearly enclosed nests which cliff swallows build. These species simply build open bowl-shaped nests which rest on the square or nearly square rectangular floors. These prior art structures accommodate single nests only, and since they are mounted singly well away from others, they do not accommodate the colonial nesting requirements of cliff swallows. The wide floors of these structures, not necessary for cliff swallows, may, however, allow undesirable birds to build their loose grass nests. Were cliff swallows to build in and nearly enclose such a structure, the interior would be inaccessible, lacking the access door of the present invention.
Finally, partial or complete artificial cliff swallow nests have been made of fired clay or concrete/earthen mixtures. Swallows will complete, or accept complete, these substitute nests. These partial or complete artificial nests in the prior art have been single nest structures which are, one by one, attached to or hung on the side of a building. An example of such an artificial nest is shown in Woodworking for Wildlife by Henderson on page 43. As individual nesting units, these cumulatively require more time to install or remove than the multiple nesting structure of the present invention. In the case of the partial artificial nests, which are essentially half bowls, placement must be close to an eave to provide the overhead protection and structure for the swallows to complete the nests. A series of these half bowls, placed linearly up close to the eave creates essentially the same situation as does the edge of a 2" by 4" board attached close to the eave. Nests are supported from below, but upper parts of the nests completed by the birds may face different directions, and so are difficult to retroactively protect from collapse as is conveniently possible with the present invention. Since both the artificial base and bird-built upper portions are attached directly to the building, the negative aspects of possible poor adhesion to building surfaces, spread of parasites into building interiors, and inaccessibility of nest interiors all apply. With the insubstantial side walls of these half bowl partial nests, cliff swallows must do substantial building to complete them, almost as when building on a mere 2".times.4" board edge base. Nest building and repairs to collapsed or partially collapsed nests can consume enough time in breeding season to limit production of young.
More nearly complete, or complete, artificial nests are also attached, one by one, in numbers to building sides or to boards nailed flat against sides of buildings. These strong structures are safe from collapse and require little building by cliff swallows. These prior art structures usually have no back wall. They are open where the back of the artificial nest meets the surface on which they are mounted. This permits cleaning through the open back when these artificial nests are removed after the breeding season. However, during the breeding season cliff swallows typically seal the small gap between the artificial nest and mounting surface, making removal disruptive. Also, since the entire nest must be handled and turned to inspect its contents, disturbed nestlings may be frightened out, and eggs may be dropped. In contrast, in the present invention, the nests remain in place while only an access door is opened for inspection with minimal disturbance to nest and contents. One major drawback to complete, or nearly complete, artificial nests is that during the off-season, destructive English sparrows will find shelter in these near enclosures. And once familiar with these nesting cavities, aggressive sparrows will kill cliff swallows for control of the cavities during breeding season. With the present invention, the front wall of mud built by migratory swallows may be easily broken out after the breeding season, so that non-migratory, destructive English sparrows are not given shelter over winter.
Finally, prior art artificial nests are costly or time-consuming to manufacture, as they are sculpted or molded complex shapes in mineral materials which must be dried, and cured or fired. The present invention permits use of more easily worked material, being wood, to manufacture cliff swallow nesting sites economically.
As discussed above, prior art devices and non-deliberately occurring prior art situations are inferior to the present invention with respect to one or more of the following considerations: acceptability by desirable cliff swallows versus undesirable species, access to nest interiors in season for inspection and control, passive and active protection of nests from collapse or inflicted damage, convenience of installation or removal, adaptability to building, bridge or post mounting, protection of mounting structures from parasite infestation or surface degradation, orderly attractiveness, and ease of manufacture, packaging and storage.